1. Field of Invention
This invention relates to a muffler system for internal combustion engines and in particular to a muffler system employing a heat exchanger to recover and utilize heat energy from exhaust gases which energy is otherwise lost to the atmosphere.
2. Description of the Prior Art
Internal combustion engines have many applications; most commonly in the automobile. In an automobile and in other uses of internal combustion engines a muffler system is connected to the exhaust port of the engine. Heat of combustion is generally dissipated to a coolant fluid which circulates around the engine and, in turn, releases the heat to the atmosphere via a radiator. Additional heat energy is simply lost to the atmosphere through escaping hot exhaust gases.
It is desirable to recover and utilize the heat energy that would otherwise be lost to the atmosphere. A conventional automobile heater does this to a certain extent by diverting the heated coolant fluid from the engine to the passenger compartment where a heat exchanger releases the heat to warm the passengers. However, the heat lost by the escape of exhaust gases is not recovered at all.
Presently known muffler devices generally have the sole goal of reducing noise. One means of achieving this is by inserting baffles which lengthen and deflect the path of exhaust gases. Another means is by cooling the gases since the wavelength of the sound explosions is dependant on the ambient temperature according to the formula: ##EQU1## where the speed of sound is directly proportional to the ambient temperature. (See eg. U.S. Pat. No. 3,630,030 issued to W. M. Wagner.) Thus, as the temperature is reduced, the speed of sound is reduced and the wavelength is reduced, enabling a shorter attenuation path required to reduce the noise.
Cooling of exhaust gas has been achieved by expanding it into various muffler chambers and by spraying the gas with a coolant fluid which then transfers the heat to the atmosphere. The ability of a coolant fluid to remove heat from the exhaust depends in part upon the surface area of coolant exposed to the gas. Known devices disperse the coolant in small droplets in an attempt to maximize the surface area exposed to collect heat.
Thus, presently known muffler devices have a primary goal of reducing engine noise by using baffles or by cooling the gases. However, the presently known cooling means have the disadvantage of wasting large amounts of heat energy which are lost to the atmosphere.